Low voltage when idling
Thread Starter
Teching In
Joined: Sep 2007
Posts: 4
Likes: 0
Low voltage when idling When idling my alternator is not charging. I have replaced it and it is still doing the same. I took the old alternator to autozone to have it checked, on their machine and it passed. I have had my battery checked twice and it is fine. After that I begin looking for other answers. I checked my ground wire and it seemed that it was a little loose, thought that might have been the problem but it is still doing the same. I am running about 800rpm idling when in park to 700 when in gear and on brake. My belt is tight. I am all out of answers or causes. Do you think it is wiring? If so where do I start or how expensive would that be to take it somewhere? Also I did buy a rebuilt alternator and when they tested both alternators they just did so at one speed, which seemed to be pretty fast. Its charges fine when I rev my engine or drive. Should I try another new one? Is it ok to drive temporary or would this hurt something else. '97 camaro Z28
Trending Topics
Originally Posted by Formula350
They make oversized Alternator pullies I thought, for when you do underdrive crank....
Last edited by dhdenney; Sep 25, 2007 at 12:24 PM.
LS1 Tech Stories
The Best V8 Stories One Small Block at Time
Gas Monkey Built a 6-Wheel Ferrari Testarossa With a Corvette LT4 Engine
Verdad Gallardo
7 Most Reliable High-Performance Engines GM Has Ever Built
Verdad Gallardo
Amazing '71 Camaro Restomod Is Modern Muscle Car Under the Skin
Verdad Gallardo
6 Common C5 Corvette Failures and What's Involved In Repairing Them
Pouria Savadkouei
Retro Modern Bandit Pontiac Trans AM Comes With Burt Reynolds' Autograph
Verdad Gallardo
Top 10 Greatest Cadillac V Series Performance Models Ever, Ranked
Pouria Savadkouei
Top 10 Most Powerful Chevy Trucks Ever Made!
Hennessey's New Supercharged Silverado ZR2 Has 700 HP
Verdad Gallardo
Coachbuilt N2A Anteros Is an LS2-Powered C6 Corvette In Italian Clothes
Verdad Gallardo
check the wire coming off the back of the alternator the heavy gauge wire.... make sure it is not cracked, burnt or stiffer than any other wire. mine was doin the same.... checked that wire and found that it was a little fried. remember as the car gets old wires do to just make sure all your output and inout vooltages are ok and u should be fine. its just an older car.
Like dhdenney caught on, it's probably the under drive pulleys. It makes the accessories run slower, including the alternator. It won't charge unless it's somewhere above 900rpm with those pulleys. Go back to stock pulleys or get a bigger alternator pulley if they make them (?).
Originally Posted by Ralls
Like dhdenney caught on, it's probably the under drive pulleys. It makes the accessories run slower, including the alternator. It won't charge unless it's somewhere above 900rpm with those pulleys. Go back to stock pulleys or get a bigger alternator pulley if they make them (?).
everyone is mistaken in order to increase the speed of the alternator you must decrease the size of the alternator pulley in relation with the crank pulley
thinks of gear ratios
if you have a crank pully that is 5 inches and an alternator pulley of one inch you are overdriving the alternator at a 5:1 ratio
so for every 1000 rpm of crank rotation the alternator spins 5000 rpm
if you go with a larger alternator pulley such as one that is 2.5 inches than you are only overdriving the alternator at a 5:2.5 ratio so for every 1000 rpm of crank rotation you spin the alternator 2500 rpm
so in other words you need a smaller alternator pulley
Originally Posted by 1994Z28Lt1
everyone is mistaken in order to increase the speed of the alternator you must decrease the size of the alternator pulley in relation with the crank pulley
thinks of gear ratios
if you have a crank pully that is 5 inches and an alternator pulley of one inch you are overdriving the alternator at a 5:1 ratio
so for every 1000 rpm of crank rotation the alternator spins 5000 rpm
if you go with a larger alternator pulley such as one that is 2.5 inches than you are only overdriving the alternator at a 5:2.5 ratio so for every 1000 rpm of crank rotation you spin the alternator 2500 rpm
so in other words you need a smaller alternator pulley
thinks of gear ratios
if you have a crank pully that is 5 inches and an alternator pulley of one inch you are overdriving the alternator at a 5:1 ratio
so for every 1000 rpm of crank rotation the alternator spins 5000 rpm
if you go with a larger alternator pulley such as one that is 2.5 inches than you are only overdriving the alternator at a 5:2.5 ratio so for every 1000 rpm of crank rotation you spin the alternator 2500 rpm
so in other words you need a smaller alternator pulley
I would check the actuater wire. the one that hooks on the side of the Alt. it pretty much tells it when to start charging. and check/clean up your grounds. underdrive/overdrive??? pullies arent goint to make you r car not charge.
Originally Posted by chromeplated500
I would check the actuater wire. the one that hooks on the side of the Alt. it pretty much tells it when to start charging. and check/clean up your grounds. underdrive/overdrive??? pullies arent goint to make you r car not charge.
